The present invention pertains generally to coolant systems and, more particularly, to a high pressure coolant system configured to provide a constant coolant pressure at a cutting tool to component interface.
In the field of production machining, it is highly desirable to construct a machining center capable of quickly and cost effectively cutting materials such as metal to precise dimensions for use in machine components. For example, general combustion engines are often times constructed from forged or cast metal components requiring a variety of machining operations to place them in condition for use within the engine.
Many manufacturers have had difficulty economically and reliably machining mass volumes of such engine components. Difficulty arises in attempting to design a coolant system capable of compensating for changes in the type of tooling used for a specific operation, the pre-machined size or location of a given surface or feature, the material properties of a specific component to be machined, the type of coolant used by a manufacturing facility, the path through which the coolant flows through the tool, the machining philosophy of the given tooling engineer and a variety of other yet to be determined factors. It should be appreciated that proper coolant flow provides a mechanism for removing chips created during the machining process and a heat transfer mechanism to dissipate energy from the cutting tool. If either of these functions are impaired, tool life and quality of cut will be negatively impacted.
One existing coolant system attempts to account for the aforementioned variables by maintaining a constant pressure at the tool to work-piece interface. The system incorporates a pressure relief valve positioned upstream from the cutting tool. An operator adjusts the pressure relief valve to define the coolant pressure at the tooling to work piece interface. However, it is unknown what flow rate is required to produce such pressure and the flow rate will vary depending on the numerous factors listed. In order to assure the requisite flow rate is present, coolant is pumped at a rate exceeding the maximum rate possibly required. As such, the system is over-designed to provide an increased flow rate to assure that some coolant is always being pumped into a reservoir. Many inefficiencies are incorporated within such a design. Specifically, the pump and the motor driving the pump are larger than necessary. The over-sized components not only cost more to purchase but also require more energy to operate than their smaller counterparts. Additionally, pumping excess flow generates heat which must be dissipated.
The existing coolant system described utilizes the pressure relief valve as an “active valve”. As an active valve, the pressure relief valve must continuously compensate for varying machining conditions in an attempt to maintain a constant pressure at the cutting tool to work-piece interface. Pressure relief valves are not commonly designed to function in this manner. Most pressure relief valves are unable to provide the system response desired. Unfortunately, a constant pressure is not maintained at the cutting interface.
In accordance with the present invention, a high pressure coolant system includes a pump, a variable speed drive and a pressure feedback control system. To maintain a constant pressure at the tool to work-piece interface, the drive mechanism speed is varied which in turn varies the pump speed to provide a known volumetric flow rate. A closed loop control varies the motor speed to maintain the desired pressure at the tool to work-piece interface.
Further areas of applicability of the present invention will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description is specific examples, while indicating preferred embodiments of the invention, are intended for purposes of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.